Internet telephony is a term used for a methodology and a set of technologies which deliver voice and multimedia telephony services over the public Internet and other networks using the Internet Protocol (IP). Other terms used include Voice over IP (VoIP) and IP telephony. Telephone calls and multimedia sessions are communicated over the underlying Internet communication protocols between telephones and other devices comprising Internet telephony application software. A term often used for an Internet telephony application is a softphone. A softphone may be used on a telephone device such as a mobile phone or cell phone, or on a fixed or portable computing device such as a tablet computer.
Interactive Voice Response (IVR) is a technology which allows human interaction with computers comprising an IVR application. The computer comprising the application is usually termed an IVR system. An IVR system accepts telephone calls from callers and can play a series of voice prompts to callers. It also have the capability to gather data from callers either through button presses or voice recognition. Many IVR systems can host a variety of applications providing different services. Typically such applications are accessible by dialing a telephone number associated with the application.
Many IVR systems now interact over Internet telephony networks. Applications in such IVR systems are often written using the VoiceXML (VXML) standard, to write IVR system voice dialogs, for example. VXML is based on XML and may interact with a voice browser of an IVR system in a way analogous to the way a textual Web browser interacts with an HTML document. A protocol frequently used for Internet telephony communication sessions is Session Initiation Protocol (SIP) which is described in Internet Engineering Task Force (IETF) Request for Comments (RFC) number rfc3261, accessible here: http://tools.ietf.org/html/rfc3261.